I wonder whether it is worse in primary schools, in a way, because the children are with the same adult all the time and therefore see them as their safe space? That could especially be the case if they have an unstable home life, which many of these children will have, and so they're lashing out with the only safe adult in their lives.
I've been working in secondary schools, many very rough ones, for close to 20 years. Verbal assault is commonplace, so is being pushed out of the way if a kid is determined to go somewhere and you're in their way. I've been threatened a few times, too, and been told (when pregnant) that the kid hopes my baby dies. All upsetting, of course. But I have never had a hand laid on me, and objects thrown my way were generally light (an exercise book, a tie). And while I'm competent, I'm certainly not Mrs Popular.
Any child assaulting a member of staff, even accidentally (a colleague once broke up a fight and was punched by one of the kids by accident), is always followed up with a severe sanction, usually exclusion for at least a day. Even in the shit schools where other behaviour incidents are tolerated way beyond what they should be.
But that's because it's very uncommon, and I wonder whether the child often doesn't have the time to build that relationship with an adult if they see them, maybe 4 times a week for an hour rather than all day, every day.
We know that most kids are worse at home than at school, because it's their safe space and thei intrinsically know they'll still be loved and accepted even if they have a meltdown.
It doesn't make it acceptable. Not in the slightest. But the issue does seem to be far worse in primary schools than in secondaries.